Refactor mainframe applications with Advanced

Azure Files
Azure Load Balancer
Azure SQL Database
Azure Storage
Azure Virtual Machines

Advanced's Automated COBOL Refactoring solution refactors COBOL applications, as well those written in CA-Gen, CA-Telon, Natural, ADSO and other legacy languages, to deliver cloud-enabled applications and databases that are functionally equivalent to their legacy counterparts. This reduces costs, allows for deeper integration, and enables customization to meet business requirements. In addition, it unlocks a whole new world of quality and scalability, from automated testing to quality assurance, and the ability to benefit from containerized deployments and orchestration with Docker and Kubernetes.

Mainframe architecture

Here's an example system where automated factoring can be used:

Architecture diagram that shows a mainframe system that includes legacy-language applications.


A. Users provide input over TCP/IP, using protocols such as TN3270, HTTP, and HTTPS.

B. Input arrives using standard mainframe protocols.

C. Batch and online applications process the input.

D. COBOL, PL/I, Assembler, and compatible languages run in an enabled environment.

E. Files and databases provide data storage. The database types include hierarchical, network, and relational.

F. Services perform tasks for the applications. Services that are commonly enabled include program execution, I/O operations, error detection, and protection.

G. Middleware and utility services manage such tasks as tape storage, queueing, output, and web support.

H. Operating systems provide the interface between the engine and the software that it runs.

I. Partitions run separate workloads, or segregate work types within the environment.

Azure architecture

This is the architecture of the example system shown above when refactored for Azure. Note that the letter callouts in the diagrams reveal where the refactored solution handles the corresponding mainframe functionality.

Architecture diagram that shows the system on Azure after refactoring.

Download a Visio file of this architecture.


  1. Input typically comes either through Azure ExpressRoute from remote clients, or from other Azure applications. In either case, TCP/IP connections are the primary means of connecting to the system. User access to web applications is over TLS port 443. You can keep the UI of the web applications the same to minimize end user retraining, or you can update it by using modern UX frameworks. Azure Bastion provides admin access to the virtual machines (VMs), maximizing security by minimizing open ports.

  2. Once in Azure, access to the application compute clusters is through an Azure load balancer. This approach allows for scale-out compute resources to process the input work. Depending on input, you can load balance at either the application level or the network-protocol level.

  3. Advanced supports deployment in containers, VMs, or Virtual Machine Scale Sets. Containers and Virtual Machine Scale Sets, unlike VMs, can scale out and in rapidly. Shifting the unit of scaling to containers optimizes infrastructure utilization.

  4. Application servers receive the input in the compute clusters, and share application state and data using Azure Cache for Redis or Remote Direct Memory Access (RDMA).

  5. Data services in the application clusters allow for multiple connections to persistent data sources. Possible data sources include:

    • Azure SQL Database.
    • Azure Cosmos DB.
    • Databases on VMs, such as Oracle and Db2.
    • Big data repositories such as Azure Databricks and Azure Data Lake.
    • Streaming data services such as Kafka and Azure Stream Analytics.
  6. The application servers host various application programs based on the language's capability, such as Java classes or COBOL programs.

  7. Data services use a combination of:

    1. High-performance storage: Azure Premium SSD and Azure Ultra Disk Storage.

    2. File storage: Azure NetApp Files and Azure Files.

    3. Standard storage: Azure Blob Storage, archive, and backup. The backup can be:

      1. Locally Redundant Storage (LRS).
      2. Zone-redundant storage (ZRS).
      3. Geo-redundant storage (GRS).
      4. Geo-zone-redundant storage (GZRS).

      For more information on redundancy, see Azure Storage redundancy.

  8. Azure platform as a service (PaaS) data services provide scalable and highly available data storage to share across multiple compute resources in a cluster. These can also be geo-redundant.

  9. Azure Data Factory can ingest data and synchronize with multiple data sources both within Azure and from external sources. Azure Blob storage is a common landing zone for external data sources.

  10. Azure Site Recovery provides for disaster recovery of the VM and container cluster components.

  11. Applications connect to private endpoints of the various PaaS services.


This example features the following Azure components. Several of these components and workflows are interchangeable or optional depending on your scenario.

  • Azure ExpressRoute extends your on-premises networks into Azure over a private, dedicated fiber connection from a connectivity provider. ExpressRoute establishes connections to Microsoft cloud services like Azure and Microsoft 365.
  • Azure Bastion provides seamless Remote Desktop Protocol (RDP) or secure shell (SSH) connectivity to virtual network VMs from the Azure portal over Transport Layer Security (TLS). Azure Bastion maximizes admin access security by minimizing open ports.
  • Azure Load Balancer distributes incoming traffic to the compute resource clusters. You can define rules and other criteria to distribute the traffic.
  • Azure Kubernetes Service (AKS) is a fully managed Kubernetes service to deploy and manage containerized applications. AKS offers serverless Kubernetes, an integrated continuous integration and continuous delivery (CI/CD) experience, and enterprise-grade security and governance.
  • Azure Virtual Machines offers many sizes and types of on-demand, scalable computing resources. With Azure VMs, you get the flexibility of virtualization without having to buy and maintain physical hardware.
  • Azure Virtual Network is the fundamental building block of Azure private networks. VMs within virtual networks can communicate securely with each other, the internet, and on-premises networks. A virtual network is like a traditional on-premises network, but with Azure infrastructure benefits like scalability, high availability, and isolation.
  • Azure Private Link provides private connectivity from a virtual network to Azure services. Private Link eliminates public internet exposure to simplify network architecture and secure the connections between Azure endpoints.
  • Azure Cache for Redis adds a quick caching layer to application architecture to handle large volumes at high speed. Azure Cache for Redis scales performance simply and cost-effectively, with the benefits of a fully managed service.
  • Azure Storage is scalable, secure cloud storage for all your data, applications, and workloads.
    • Azure Disk Storage is high-performance, durable block storage for business-critical applications. Azure managed disks are block-level storage volumes that are managed by Azure on Azure VMs. The available types of disk storage are Ultra Disk Storage, Premium SSD, Standard SSD, and Standard HDD. This architecture uses either Premium SSD or Ultra Disk Storage.
    • Azure Files offers fully managed file shares in the cloud that are accessible via the industry standard Server Message Block (SMB) protocol. Cloud and on-premises Windows, Linux, and macOS deployments can mount file shares concurrently.
    • Azure NetApp Files provides enterprise-grade Azure file shares that are powered by NetApp. Azure NetApp Files makes it easy for enterprises to migrate and run complex, file-based applications with no code changes.
    • Azure Blob Storage is scalable and secure object storage for archives, data lakes, high-performance computing, machine learning, and cloud-native workloads.
  • Azure databases offer a choice of fully managed relational and NoSQL databases to fit modern application needs. Automated infrastructure management provides scalability, availability, and security.
    • Azure SQL Database is a fully managed PaaS database engine. SQL Database always runs on the latest stable version of SQL Server and a patched OS with high availability. Built-in PaaS database management capabilities include upgrading, patching, backups, and monitoring. You can focus on domain-specific, business-critical database administration and optimization.
    • Azure Database for PostgreSQL is a fully managed database based on the open-source PostgreSQL relational database engine. The Hyperscale (Citus) deployment option scales queries across multiple machines by using sharding, for applications that require greater scale and performance.
    • Azure Cosmos DB is a fully managed, fast NoSQL database with open APIs for any scale.
  • Azure Site Recovery mirrors Azure VMs to a secondary Azure region for quick failover and data recovery if an Azure datacenter fails.
  • Azure Data Factory is an extract, transform, and load (ETL) service for scale-out, serverless data integration and data transformation. It offers a code-free UI for intuitive authoring and single-pane-of-glass monitoring and management.

Scenario details

There are many reasons to look for alternatives to the COBOL-based mainframe applications that are still common:

  • COBOL and CA-Gen/Natural/Telon/ASDO developers are retiring and no one is trained to replace them, resulting in a steadily diminishing talent pool. As the talent shortage grows, the costs and risks of relying on COBOL and other legacy languages increase.
  • The applications weren't designed for modern IT, resulting in difficult integrations and limited flexibility.
  • IBM mainframe hardware and software are expensive, and licensing and maintenance fees for ancillary mainframe applications and databases are rising.

Advanced's Automated COBOL Refactoring solution refactors COBOL applications, as well those written other legacy languages, to deliver cloud-enabled applications and databases that are functionally equivalent to their legacy counterparts. This reduces costs, allows for deeper integration, and enables customization to meet business requirements. In addition, it unlocks a whole new world of quality and scalability, from automated testing to quality assurance, and the ability to benefit from containerized deployments and orchestration with Docker and Kubernetes.

The refactored applications:

  • Are functionally equivalent to the originals.
  • Are easy to maintain—they attain SonarQube A ratings, and follow object-oriented concepts and paradigms.
  • Perform as well as, or better than, the originals.
  • Are cloud-ready and delivered by using a standard DevOps toolchain and best practices.

The refactoring process includes flow normalization, code restructuring, data layer extraction, data remodeling, and packaging for reconstruction. The process identifies cloned code and creates shared replacement objects, simplifying maintenance and manageability. Complex data and control dependency analysis locates and removes dead code.

Once the Advanced solution refactors the COBOL applications and associated databases, Java and C# developers can use standard DevOps tools and CI/CD concepts to extend application functionality. The refactoring process preserves business logic and optimizes performance. Additional benefits include elasticity, granular service definition, and easy integration with cloud-native services.

Automated COBOL Refactoring is available for most COBOL dialects and platforms, including z/OS, OpenVMS, and VME.

Potential use cases

Advanced refactoring benefits many scenarios, including:

  • Businesses seeking to:
    • Modernize infrastructure and escape the exorbitant costs, limitations, and rigidity associated with mainframes.
    • Avoid the risk associated with skills shortages around legacy systems and applications by going cloud-native and DevOps.
    • Reduce operational and capital expenditure costs.
  • Organizations wanting to migrate mainframe workloads to the cloud without costly and error-prone manual rewrites.
  • Organizations that need to migrate business-critical applications while maintaining continuity with other on-premises applications.
  • Teams looking for the horizontal and vertical scalability that Azure offers.
  • Businesses that favor solutions that have disaster recovery options.


Incorporate the following pillars of the Microsoft Azure Well-Architected Framework for a highly available and secure system:



Refactoring not only supports faster cloud adoption, but also promotes adoption of DevOps and Agile working principles. You have full flexibility in development and production deployment options.


This solution uses an Azure network security group to manage traffic between Azure resources. For more information, see Network security groups.

Private Link for Azure SQL Database provides a private, direct connection that's isolated to the Azure networking backbone from the Azure VMs to Azure SQL Database.

Azure Bastion maximizes admin access security by minimizing open ports. Bastion provides secure and seamless RDP/SSH connectivity to virtual network VMs directly from the Azure portal over TLS.


Resiliency is built into this solution by the load balancers. If one presentation or transaction server fails, other servers behind the load balancers can run the workloads according to the rules and health probes. Availability sets and geo-redundant storage are highly recommended.

Cost optimization

Azure avoids unnecessary costs by identifying the correct number of resource types, analyzing spending over time, and scaling to meet business needs without overspending.

  • Azure provides cost optimization by running on VMs. You can turn off the VMs when they're not in use, and script a schedule for known usage patterns. See the Azure Well-Architected Framework for more information about cost optimization for VM instances.
  • The VMs in this architecture use either Premium SSD or Ultra Disk Storage. For more information about disk options and pricing, see Managed Disks pricing.
  • SQL Database optimizes costs with serverless compute and Hyperscale storage resources that automatically scale. For more information about SQL Database options and pricing, see Azure SQL Database pricing.
  • Use the Pricing calculator to estimate costs for your implementation of this solution.


This article is maintained by Microsoft. It was originally written by the following contributors.

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